Apparatus for fuel nozzle staging for gas turbine engines

ABSTRACT

A fuel delivery system for fuel nozzle staging includes a gas circuit and a fuel circuit. Each circuit includes a first manifold and a second manifold. The fuel delivery system delivers a first gas and a first fuel to a gas turbine engine during initial operation through the first manifold connected within each respective gas circuit. As the gas turbine engine reaches a predetermined operational speed, staging valves permit the fuel delivery system to also deliver the first gas and the first fuel to the gas turbine engine through the second manifold of each respective gas circuit.

This application is a divisional of U.S. application Ser. No.09/434,343, filed Nov. 5, 1999 which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

This invention relates generally to gas turbine engines and, moreparticularly, to fuel delivery systems for fuel nozzle staging for gasturbine engines.

Controlling a pressure ratio of fuels delivered to a dual fuel gasturbine engine is critical for the engine's performance. Typically, dualfuel gas turbine engines exhibit operability limitations during normalengine starts and during engine low power operating conditions. Forexample, undesirable engine flameouts are prevalent in gas turbineengines supplied with gas and steam premix, or dual fuel (gas andliquid), and in steam premix turbines as a result of the low fuel flowrates supplied during start conditions. Additionally, flameouts mayoccur at steady state fuel flow conditions in gas turbine engines whenlow pressure differentials develop at the fuel nozzle tips, i.e., singleannular combustor (SAC) fuel configuration.

To compound the flammability problem, typically the performance of gasturbine engine fuel delivery systems are optimized to be withinacceptable performance ranges when the gas turbine engines are operatingat maximum fuel flow conditions. While optimizing a fuel delivery systemto perform at maximum fuel flow conditions enhances the performance ofthe gas turbine engine during high fuel flow conditions, it alsoincreases the possibility of flameouts during low fuel flow conditions.Fuel nozzle pressures can be raised to alleviate flammabilityoperability regions of the engine. However, raising the fuel nozzlepressures to improve the flammability levels at low fuel flow conditionsmay cause excessive and damaging pressures at maximum fuel flowconditions, where the engine operates more frequently. Additionally,optimizing the fuel delivery systems at low fuel flow conditions mayincrease carbon monoxide emission levels generated by the gas turbineengine, thus creating potential environmental issues.

BRIEF SUMMARY OF THE INVENTION

In an exemplary embodiment, a fuel delivery system for fuel nozzlestaging is provided for use with a gas turbine engine. The fuel deliverysystem includes two circuits. A gas circuit delivers fuel to the gasturbine engine, and includes a primary manifold and a secondarymanifold. A steam circuit delivers steam to the gas turbine engine andincludes a primary manifold and a secondary manifold. Both the gascircuit and the steam circuit are connected to a plurality of fuelnozzles which include primary fuel nozzles and secondary fuel nozzles.Additionally, both circuits include a staging valve to control the flowof each respective gas and steam into each respective circuit's secondmanifold.

During operation, the gas circuit primary manifold and the steam circuitprimary manifold deliver fuel and steam respectively to the gas turbineengine during initial operation and idle operation of the gas turbineengine. During initial operations and idle operations, the primary fuelnozzles deliver the first fuel and steam to the gas turbine engine. Oncethe gas turbine engine reaches a predetermined operational speed, thestaging valves open and direct fuel and steam into the secondary fuelnozzles. As a result of such fuel nozzle staging, the fuel and controlsystem eliminates more detrimental fuel delivery systems and provides auser with a fuel delivery system which improves flammability limits,accurately controls the delivery of fuel, and provides flexibility tothe user.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a fuel delivery system foroperating a fuel nozzle staging for a gas turbine engine; and

FIG. 2 is a side elevational view of one embodiment of a dual fuelnozzle that could be used in conjunction with the fuel delivery systemshown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic illustration of a fuel delivery system 10 for fuelnozzle staging for a gas turbine engine (not shown). Fuel deliverysystem 10 includes a steam circuit 12 and a gas circuit 14 whichrespectively deliver a first gas, i.e. steam, and a first fuel, i.e.gas, to the gas turbine engine. Steam circuit 12 and gas circuit 14 areboth metered and sized to achieve a pressure ratio within fuel deliverysystem 10 appropriate for the fluid being delivered to the gas turbineengine. Steam circuit 12 delivers a metered steam flow to the gasturbine engine and gas circuit 14 delivers a metered fuel flow to thegas turbine engine.

Steam circuit 12 includes a connecting line 16 which extends from ametering valve (not shown) to a primary manifold 20. The metering valveis positioned between a steam supply source (not shown) and connectingline 16. The operation of a metering valve for controlling a flow ofsteam is well known. Manifold 20 is connected to a connecting line 22which extends from manifold 20 to a fuel nozzle sub-system 23 andincludes a plurality of fuel nozzles 24. In one embodiment, manifold 20is a primary steam manifold. Fuel nozzles 24 are connected to the gasturbine engine and deliver steam to the gas turbine engine duringinitial operation of the engine and while the gas turbine engine isoperating at an idle speed. In one embodiment, fuel nozzles 24 areprimary fuel nozzles and are available from Parker Hannifin, 6035Parkland Blvd., Cleveland, Ohio.

A connecting line 30 is connected to connecting line 16 between manifold20 and the steam circuit metering valve. The steam circuit meteringvalve is connected between the steam supply source and connecting line16, upstream of a connection 31 with line 30. Connecting line 30 extendsfrom connecting line 16 to a staging valve 32. Staging valve 32 controlsthe flow of steam from connecting line 16 to a secondary manifold 34.Staging valve 32 is sized to accommodate a maximum steam flow forsecondary manifold 34 for a secondary steam flow being supplied by fueldelivery system 10. In one embodiment, secondary manifold 34 is asecondary steam manifold. Secondary manifold 34 is connected to aconnecting line 36 which extends from secondary manifold 34 to aplurality of fuel nozzles 38 of fuel sub-system 23. Fuel nozzles 38 areconnected to the gas turbine engine and deliver the secondary steam andsecondary gas flows to the gas turbine engine once the gas turbineengine has been operating for a predetermined length of time and isbeing accelerated from the initial idle speed. In one embodiment, fuelnozzles 38 are secondary fuel nozzles and are available from ParkerHannifin, 6035 Parkland Blvd., Cleveland, Ohio.

Gas circuit 14 includes a connecting line 50 which extends from ametering valve (not shown) to a primary manifold 52. The metering valveis positioned between a fuel supply source (not shown) and connectingline 50. In one embodiment, the fuel supply source is a natural gassupply source. Manifold 52 is connected to a connecting line 54 whichextends from manifold 52 to a plurality of fuel nozzles 56 of fuelsub-system 23. In one embodiment, manifold 52 is a primary gas manifold.Fuel nozzles 56 are connected to the gas turbine engine to deliver thefirst fuel to the engine during initial operation of the gas turbineengine and while the gas turbine engine is operating at an idle speed.In one embodiment, fuel nozzles 56 are primary fuel nozzles and areavailable from Parker Hannifin, 6035 Parkland Blvd., Cleveland, Ohio.

A connecting line 60 is connected to connecting line 50 between manifold52 and the gas circuit metering valve. The gas circuit metering valve isconnected between the fuel supply source and connecting line 50,upstream of a connection 61 with line 60. Connecting line 60 extendsfrom connecting line 50 to a staging valve 62. Staging valve 62 controlsthe flow of the fuel from connecting line 50 to a secondary manifold 66.Staging valve 62 is sized to accommodate a maximum flow for secondarymanifold 66 for the second fuel being supplied by fuel delivery system10. In one embodiment, secondary manifold 66 is a secondary gasmanifold. Secondary manifold 66 is connected to a connecting line 68which extends from manifold 66 to a plurality of fuel nozzles 70 of fuelsub-system 23. Fuel nozzles 70 are connected to the gas turbine engineand deliver the fuel to the gas turbine engine once the gas turbineengine has been operating with a predetermined load at a predeterminedpower level and is being accelerated from the initial synchronous idlespeed. In one embodiment, fuel nozzles 70 are secondary fuel nozzles andare available from Parker Hannifin, 6035 Parkland Blvd., Cleveland,Ohio.

In operation, fuel delivery system 10 is capable of delivering the steamand fuel such that the gas turbine engine is capable of starting using ametered gas flow. To start the gas turbine engine, fuel delivery system10 stages the metered gas flows between primary nozzles 24 and 56. Inone embodiment, fuel delivery system 10 includes 20 primary nozzles 24and 56. During the gas turbine engine start and during low power modesand idle power modes, the first fuel and steam are delivered to the gasturbine engine through primary manifolds 20 and 52 to primary fuelnozzles 24 and 56 respectively. While the first fuel and steam are beingdelivered to primary manifolds 20 and 52, staging valves 32 and 62 areclosed to prevent the fuel and the steam from being delivered tosecondary manifolds 34 and 66. Delivering the first fuel and steamthrough primary nozzles 24 and 56 during low power conditions and idleoperations of the gas turbine engine enhances a low pressure ratio offuel delivery system 10 which improves flammability limits for the gasturbine engine. Additionally, it has been determined that fuel andcontrol system 10 may reduce such emission levels up to four timesgreater than known non-premix fuel and control systems.

In an alternative embodiment, staging valve 32 and staging valve 62provide a pilot flow when staging valves 32 and 62 are in a fully closedposition (not shown). The pilot flow provides a minimum positive gasflow to manifolds 34 and 66 to prevent potentially damaging combustiongases from back-flowing from the gas turbine engine into manifolds 34and 66.

The gas turbine engine is then accelerated from synchronous idleoperation. Once the engine reaches a predetermined operational speed,fuel delivery system 10 directs gas flow to secondary manifolds 34 and66 by gradually opening steam circuit staging valve 32 and gas circuitstaging valve 62. As staging valves 32 and 62 are opened, the first fueland steam are directed into manifolds 34 and 66 respectively.Simultaneously, the first fuel and steam are still being directed intoprimary fuel nozzles 24 and 56 through manifolds 20 and 52 respectively.Shortly thereafter, secondary steam and gas flows from secondary fuelnozzles 38 and 70 respectively and into the gas turbine engine. In oneembodiment, fuel delivery system 10 includes 10 secondary fuel nozzles38 and 70. Simultaneously, the steam and the first fuel are still beingdirected into primary fuel nozzles 24 and 56 through manifolds 20 and 52respectively.

FIG. 2 is a side elevational view of one embodiment of a dual fuelnozzle 80 that could be used in conjunction with fuel and control system10. Fuel nozzle 80 is similar to fuel nozzles 24, 38, 56, and 70 (shownin FIG. 1). In one embodiment, fuel nozzles 24, 38, 56, and 70 are eachthe same model fuel nozzle and have the same set of performance flowcharacteristics at all power operations. Therefore, the gas turbineengine exit temperature pattern factors and profiles are retained as theengine is accelerated and secondary fuel nozzles 38 and 70 deliver thegas and steam to the gas turbine engine.

Nozzle 80 includes a gas inlet 82, a steam inlet 83, a nozzle body 84,and a nozzle tip 86. Nozzle body 84 has a first end 88 and a second end90. Inlet 82 is positioned adjacent first end 88 and nozzle tip 86 ispositioned adjacent second end 90. Inlet 82 extends from nozzle body 84and includes a coupling 92 which permits a connection to fuel circuitconnection line 68 (shown in FIG. 1) or fuel circuit connection line 54.(shown in FIG. 1). Additionally, inlet 82 includes an elbow block 94which connects coupling 92 to nozzle body 84. As first fuel flowsthrough connecting lines 54 and 68 into coupling 92, elbow 94 directsthe first fuel flow from coupling 92 towards nozzle body 84.

Steam inlet 83 extends from a coupling 98 attached to nozzle body 84.Coupling 98 connects nozzle 80 to steam circuit connecting line 22(shown in FIG. 1) or steam circuit connecting line 36 (shown in FIG. 1).The steam enters steam inlet 83 in a direction 102 which issubstantially parallel to a direction 103 in which the first fuel entersgas inlet 82. Once within nozzle body 84, the first fuel is mixed withthe steam and directed towards nozzle tip 86.

The above described fuel delivery system for fuel nozzle staging for agas turbine engine is cost-effective and reliable. The system includes agas circuit and a fuel circuit wherein each circuit includes a primarymanifold and a secondary manifold. The fuel delivery system delivers asteam and a first fuel to a turbine engine during initial operationthrough a plurality of primary fuel nozzles. Once the engine reaches apredetermined operational speed, the fuel delivery system also deliversthe steam and the first fuel to the gas turbine engine through aplurality of secondary fuel nozzles. Accordingly, a fuel delivery systemis provided for fuel nozzle staging for a gas turbine engine whicheliminates more costly fuel delivery systems and provides a user with areliable, flexible, and accurate fuel delivery system for a gas turbineengine.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

What is claimed is:
 1. A fuel and control system for a gas turbineengine, said fuel and control system comprising a fuel delivery systemcomprising: at least two manifolds comprising a first primary manifoldand a second primary manifold, said first primary manifold for supplyingto the gas turbine engine steam during initial operation of the gasturbine engine, said second primary manifold for supplying to the gasturbine engine fuel during initial operation of the gas turbine engine;and a fuel nozzle sub-system connected to said manifolds, said fuelnozzle sub-system comprising a plurality of primary fuel nozzles and aplurality of secondary fuel nozzles, said primary fuel nozzles receivesteam and fuel during initial operation of the gas turbine engine.
 2. Afuel and control system in accordance with claim 1 further comprising afirst secondary manifold for supplying steam to the gas turbine engineonce the gas turbine engine has operated at a predetermined power levelwith a predetermined load.
 3. A fuel and control system in accordancewith claim 2 further comprising a second secondary manifold forsupplying fuel to the gas turbine engine once the gas turbine engine hasoperated at the predetermined power level.
 4. A fuel and control systemin accordance with claim 3 further comprising a plurality of stagingvalves for controlling a flow of steam and a flow of fuel.
 5. A fuel andcontrol system in accordance with claim 3 , wherein said secondary fuelnozzles receive steam and fuel after the gas turbine engine has operatedat the predetermined power level.
 6. A fuel and control system inaccordance with claim 1 wherein said plurality of primary fuel nozzlescomprises 20 primary fuel nozzles, said plurality of secondary fuelnozzles comprises 10 secondary fuel nozzles.
 7. A fuel and controlsystem in accordance with claim 4 wherein said plurality of stagingvalves comprises a first staging valve and a second staging valve.
 8. Afuel and control system in accordance with claim 7 wherein said firststaging valve controls a flow of fuel to said second secondary manifold.9. A fuel and control system in accordance with claim 7 wherein saidsecond staging valve controls a flow of steam to said first secondarymanifold.
 10. A fuel and control system for a gas turbine engine, saidfuel and control system comprising a fuel delivery system comprising: asteam circuit for supplying steam to the gas turbine engine, said steamcircuit comprising a primary manifold and a secondary manifold, saidprimary manifold for supplying steam during initial operation of the gasturbine engine; and a fuel circuit for supplying fuel to the gas turbineengine, said fuel circuit comprising a primary manifold and a secondarymanifold, said fuel circuit primary manifold for supplying fuel duringinitial operation of the gas turbine engine.
 11. A fuel and controlsystem in accordance with claim 10 wherein said steam circuit furthercomprises a plurality of nozzles connected to said steam circuit primarymanifold and said steam circuit secondary manifold, and a staging valveconnected to said steam circuit secondary manifold, said steam circuitsecondary manifold for supplying steam to the gas turbine engine oncethe gas turbine engine has operated at a predetermined power level witha predetermined load, said staging valve for controlling a flow of steamto said steam circuit secondary manifold.
 12. A fuel and control systemin accordance with claim 11 wherein said fuel circuit further comprisesa plurality of nozzles connected to said fuel circuit primary manifoldand said fuel circuit secondary manifold, and a staging valve connectedto said fuel circuit secondary manifold, said secondary manifold forsupplying fuel to the gas turbine engine once the engine has operatedthe predetermined power level, said staging valve for controlling a flowof fuel to said fuel circuit secondary manifold.
 13. A fuel and controlsystem in accordance with claim 12 wherein said steam circuit pluralityof nozzles comprises a plurality of primary nozzles and a plurality ofsecondary nozzles, said fuel circuit plurality of nozzles comprises aplurality of primary nozzles and a plurality of secondary nozzles.
 14. Afuel and control system in accordance with claim 13 wherein said steamcircuit plurality of primary nozzles and said fuel circuit plurality ofprimary nozzles comprise 20 primary nozzles, said steam circuitplurality of secondary nozzles and said fuel circuit of secondarynozzles comprise 10 secondary nozzles.